1. Technical Field
The present invention relates to a liquid crystal display (LCD) device and a driving method for the same and in particular, relates to an IPS (in-plane-switching) mode LCD device and the driving method for the same.
2. Background Art
In recent years, a liquid crystal display (LCD) device with a wide viewing angle has been developed. An IPS (in-plane-switching) mode is one of the methods for realizing a wide viewing angle of the LCD device. In the IPS mode LCD device, comb-shaped electrodes are formed only on a surface of one substrate of a pair of substrates which an LCD panel has, and a liquid crystal is driven by a transverse electric field parallel to the both substrates. In this IPS mode, when an electric field is applied to a liquid crystal, a liquid crystal molecule rotates in parallel with the substrate. Therefore, even when seen from every viewing angle, a refractive index change in the liquid crystal molecule hardly occurs and a desired image is obtained with a wide viewing angle. For this reason, this IPS mode is noted from a view of a super-wide viewing angle recently.
FIG. 23 is a plan view of a TFT substrate 1001 provided in a related IPS mode LCD device 1000 (FIG. 24), and FIG. 24 and FIG. 25 are cross sectional views of the LCD device 1000. FIG. 24 is a cross sectional view of a part corresponding to the line XXIV-XXIV in FIG. 23, and FIG. 25 is a cross sectional view of a part corresponding to the line XXV-XXV in FIG. 23. In FIG. 23, an alignment film 1012 and a second insulating film 1010 mentioned later are not illustrated.
As shown in FIG. 24 and FIG. 25, the LCD device 1000 is provided with a TFT substrate 1001 and a color filter substrate 1002 opposing the TFT substrate 1001. The color filter substrate 1002 is stuck on the TFT substrate 1001, and a liquid crystal layer 1003 is inserted therebetween.
The TFT substrate 1001 includes a flat glass substrate 1004 with a scanning line 1007 and a common electrode wiring 1015 formed thereon, a first insulating layer 1005 formed on the glass substrate 1004 so as to cover the scanning lines 1007 and the common electrode wiring 1015, a data line (signal line) 1008, a pixel electrode 1009 and a thin-film transistor (TFT) 1014 which are formed on the first insulating layer 1005, a second insulating layer 1010 formed on the first insulating layer 1005 so as to cover the data lines 1008 and the thin-film transistor 1014, a common electrode 1011 formed on the second insulating layer 1010, and an alignment film 1012 formed on the second insulating layer 1010 to cover the common electrode 1011.
The scanning line 1007 and the common electrode wiring 1015 extend in a row direction (an X direction of FIG. 23), respectively, and several these lines are formed with a predetermined interval. The data line 1008 extends in a column direction (a Y direction of FIG. 23) which intersects perpendicularly to the row direction, and several these lines are formed with a predetermined interval. The scanning line 1007, the data line 1008, and the common electrode wiring 1015 are composed of metallic films, for example.
The pixel electrode 1009 is composed of comb-shaped pixel electrode comb-teeth 1009A, and a storage capacitance formation part 1009B which forms a capacitance with the common electrode 1011. The storage capacitance formation part 1009B is located on the common electrode wiring 1015. As shown in FIG. 23, the pixel electrode comb-tooth 1009A is located in a display area 1013 which is inserted between the common electrode wiring 1015 and the scanning line 1007, and is inserted between the adjacent data lines 1008. The pixel electrode comb-teeth 1009A are electrically connectable with the data line 1008 via the thin-film transistor 1014.
The storage capacitance formation part 1009B extends in a row direction so that a part of the common electrode wiring 1015 is covered with it.
The common electrode 1011 includes a latticed part 1011A and common electrode comb-teeth 1011B. The latticed part 1011A has an approximately latticed shape pattern, which is arranged to cover the data line 1008 and the common electrode wiring 1015 and the display area 1013 is surrounded therewith. The common electrode comb-tooth 1011B has a shape of a comb-tooth, and is projected into the display area 1013 out of a part in the latticed part 1011A which covers the common electrode wiring. 1015.
On the other hand, the color filter substrate 1002 includes a flat glass substrate 1020, a black matrix layer 1021 formed on the glass substrate 1020, a color layer 1022 formed on the glass substrate 1020 so as to cover the black matrix layer 1021, and an alignment film 1024 formed on the color layer 1022. The black matrix layer 1021 is formed in a plane shape of an approximately latticed shape so as to oppose and cover the data line 1008, the scanning line 1007 and the common electrode wiring 1015 on the TFT substrate 1001. The black matrix layer 1021 has a light-shielding function.
Japanese Patent Application Laid-Open Hei 11-231344 discloses another type of an IPS mode LCD device in which a first common electrode and a pixel electrode are arranged on an array substrate so that a transverse electric field can be produced and a second common electrode opposing the first common electrode of the array substrate is formed on a counter substrate.